X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Reexamination Certificate
2001-06-29
2003-03-04
Bruce, David V. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
C378S004000, C378S019000
Reexamination Certificate
active
06529576
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to methods and apparatus for image reconstruction, and more particularly to methods and apparatus for adaptive image reconstruction for helical scans in multislice computed tomographic imaging systems.
Because of the non-robustness of multisector reconstruction methods, single sector reconstruction methods are often selected for cardiac computed tomographic (CT) imaging. In this reconstruction mode, a channel-dependent linear interpolation is used to estimate a set of projections at a plane of reconstruction (POR). The resulting projections are then weighted by a halfscan algorithm prior to filtering and backprojecting.
Investigations have revealed that slice sensitivity profiles (SSPs) for such reconstructions are significantly degraded at lower helical pitches. In particular, degraded contrast for small structures and an increased effect of partial volume have been noted.
BRIEF SUMMARY OF THE INVENTION
There is therefore provided, in one embodiment of the present invention, a method for reconstructing an image of an object utilizing a computed tomographic imaging system having a rotating gantry, a multirow detector array on the rotating gantry, and a radiation source on the rotating gantry configured to project a beam of radiation towards the detector array through an object to be imaged. The method includes helically scanning an object at a selected helical pitch to acquire projection data of the object, the projection data including conjugate samples from single rows of the detector array and interrow samples; estimating projections in a plane of reconstruction (POR) based upon a selection of the projection data from the group consisting of the conjugate samples from at least one of the single rows, the interrow samples, and combinations thereof, the selection dependent upon the selected helical pitch; and filtering and backprojecting the estimated projections to reconstruct at least one image of the object.
There is also provided, in another embodiment of the present invention, a method for reconstructing an image of an object utilizing a computed tomographic imaging system having a rotating gantry, a multirow detector array on the rotating gantry, and a radiation source on the rotating gantry configured to project a beam of radiation towards the detector array through an object to be imaged. The method includes helically scanning an object at a selected helical pitch to acquire projection data of the object, the projection data including conjugate samples from single rows of the detector array and interrow samples; estimating projections in a plane of reconstruction based upon a selection of the projection data from the group consisting of the conjugate samples from at least one of the single rows, the interrow samples, and combinations thereof, the selection dependent upon the selected helical pitch; weighting samples of the projection data according to a distance between a corresponding conjugate sampling pair and corresponding interrow sampling pair when a combination of the conjugate samples from at least one of the single rows and the interrow samples is selected; and filtering and backprojecting the weighted samples to reconstruct at least one image of the object.
In yet another embodiment of the present invention, there is provided a method for reconstructing an image of an object utilizing a computed tomographic imaging system having a rotating gantry, a multirow detector array oil the rotating gantry, and a radiation source on the rotating gantry configured to project a beam of radiation towards the detector array through an object to be imaged. This embodiment includes helically scanning an object at a selected helical pitch to acquire projection data of the object, the projection data including conjugate samples from single rows of the detector array and interrow samples; reconstructing an image of the object utilizing the conjugate samples; reconstructing an image of the object utilizing the interrow samples; and combining the image reconstructed utilizing the conjugates samples and the image reconstructed utilizing the interrow samples according to a pitch-dependent weighting function.
In still another embodiment, the present invention provides a computed tomographic imaging system having a rotating gantry, a multirow detector array on the rotating gantry, and a radiation source on the rotating gantry configured to project a beam of radiation towards the detector array through an object to be imaged. The system is configured to helically scan an object at a selected helical pitch to acquire projection data of the object, the projection data including conjugate samples from single rows of said detector array and interrow samples; and estimate projections in a plane of reconstruction based upon a selection of the projection data from the group consisting of the conjugate samples from at least one of the single rows, the interrow samples, and their combination, the selection dependent upon the selected helical pitch; and filter and backproject the estimated projections to reconstruct at least one image of the object.
Yet another embodiment of the present invention provides a computed tomographic imaging system having a rotating gantry, a multirow detector array on the rotating gantry, and a radiation source on the rotating gantry configured to project a beam of radiation towards the detector array through an object to be imaged. The system is configured to helically scan an object at a selected helical pitch to acquire projection data of the object, the projection data including conjugate samples from single rows of the detector array and interrow samples; estimate projections in a plane of reconstruction based upon a selection of the projection data from the group consisting of the conjugate samples from at least one of the single rows, the interrow samples, and combinations thereof, the selection dependent upon the selected helical pitch; weight samples of the projection data according to a distance between a corresponding conjugate sampling pair and corresponding interrow sampling pair when a combination of the conjugate samples from at least one of the single rows and the inter-row samples is selected; and filter and backproject the weighted samples to reconstruct at least one image of the object.
In yet another embodiment of the present invention, there is provided a computed tomographic imaging system having a rotating gantry, a multirow detector array on the rotating gantry, and a radiation source on the rotating gantry configured to project a beam of radiation towards the detector array through an object to be imaged. The system is configured to helically scan an object at a selected helical pitch to acquire projection data of the object, the projection data including conjugate samples from single rows of the detector array and interrow samples; reconstruct an image of the object utilizing the conjugate samples; reconstruct an image of the object utilizing the interrow samples; and combine the image reconstructed utilizing the conjugates samples and the image reconstructed utilizing the interrow samples according to a pitch-dependent weighting function.
Still another embodiment of the present invention provides a device for reconstructing an image of an object utilizing projection data acquired from a helical scan of the object at a selected pitch utilizing a computed tomographic imaging system having a multislice detector array with a plurality of rows, the projection data including both conjugate samples from single rows of the detector array and interrow samples. The device is configured to estimate projections in a plane of reconstruction based upon a selection of the projection data from the group consisting of the conjugate samples from at least one of the single rows, the interrow samples, and combinations thereof, the selection dependent upon the selected helical pitch; and filter and backproject the estimated projections to reconstruct at least one image of the object.
In another emb
Acharya Kishore C.
Hsieh Jiang
Armstrong Teasdale LLP
Bruce David V.
GE Medical Systems Global Technology Company LLC
Horton Esq. Carl B.
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